The coupling of bay hydrodynamics to sediment transport and its implication in micro-tidal wetland sustainability

To investigate bay hydrodynamics and its impacts on the adjacent micro-tidal wetland sustainability, hourly measurements of wave, tidal current, and benthic suspended sediment concentration in summer, winter, and spring of 2015-2016 were conducted in Fourleague Bay, Louisiana, USA. High-temporal resolution data indicate that benthic suspended sediment resuspension had a dominant periodicity of 4.8-d, which was mainly caused by wind-driven waves. Sediment flux reached 28 g·m−2·s−1 during events. Net sediment flux direction is northwestward in summer, and southeastward in winter and spring. Potential depth-integrated sediment flux to surrounding wetland varied within 0-500 g·m−1·s−1. Seasonal variations of river discharge and wind direction (particularly speed >3 m·s−1) dominated potential sediment contribution from the bay to the surrounding wetland. Three sediment transport regimes were delineated: 'bypassing' season, resuspension-accumulation season, and combined 'bypassing' and resuspension-accumulation season. This study couples bay hydrodynamics to the sediment transport processes and sustainability of adjacent wetlands in a micro tidal environment. It sheds light on the understanding of natural feedback mechanisms and how estuarine-marsh system survive high relative sea level rising scenario in micro tidal environment, which could aid in the design of future ecological engineering restoration strategies.